Enzymes

Question 1

What are enzymes, and what are they made of?

Answer 1

Enzymes are globular proteins that act as biological catalysts for chemical reactions within cells. They are composed of polypeptide chains and amino acids.

Question 2

Are enzymes impacted by the reaction they catalyse?

Answer 2

No, enzymes remained unchanged by the reaction

Question 3

What is the active site, and substrate of an enzyme?

Answer 3

A substrate is the reactant of the reaction being catalysed. The active site is the part of the enzyme where the substrate(s) bind. This binding forms a substrate-enzyme complex. Enzymes are specific to a particular substrate.

Question 4

How does an enzyme catalyse a reaction?

Answer 4

It lowers the activation energy required for the reaction to take place. It brings the necessary substrates together for the reaction much faster than by themselves.

Question 5

Describe the first model of enzyme activity

Answer 5

The ‘lock and key’ model assumes the active site is rigid and perfectly fits the substrate.

Question 6

Describe the current model of enzyme activity

Answer 6

The induced fit model suggests that the binding of the substrate induces the enzyme to alter its shape slightly to fit more tightly around the substrate.

Question 7

What is meant by the ‘denaturing’ of the enzyme?

Answer 7

Denaturing occurs when the enzyme loses its shape and its ability to bind a substrate completely. This occurs in sub-optimal pH levels or temperatures.

Question 8

What is a catabolic enzyme?

Answer 8

Breaks down molecules into simpler ones (digestive system)

Question 9

What is an anabolic enzyme?

Answer 9

Join two smaller molecules into one (used in photosynthesis)

Question 10

What is a co-enzyme?

Answer 10

Enzymes that assist other enzymes.

Question 11

What is a co-factor?

Answer 11

An inorganic material that assists enzymes (eg. zinc ion)

Question 12

How does substrate concentration affect enzyme activity?

Answer 12

The rate of reaction increases as substrate concentration increases, but rate of reaction plateaus at maximum (reaches saturation point).

Question 13

How does temperature affect enzyme activity?

Answer 13

Enzymes function normally at 40. In humans, 37.
After the optimum temperature is reached, enzyme activity decreases until it denatures at 50-60.
Excessive cold can slow rate of reaction, but does not cause denaturing.

Question 14

How does pH affect enzyme activity?

Answer 14

Each enzyme has a different optimum pH range. pH levels outside this range will denature the enzyme. In most cells, enzymes function at pH 7